Upload a FLAC file and get a AAC back. No signup, no watermark, no limit on how many.
FLAC compresses losslessly: it typically halves a WAV and gives back bit-for-bit the same audio when decoded. It is free, open, and widely supported outside Apple's world.
Where you run into it: Archived rips, Bandcamp and Qobuz downloads, anyone who keeps a music library they intend to still have in ten years.
What it costs you: Half of enormous is still large, and some hardware — car head units especially — will not touch it.
AAC is MP3's designated successor and wins at low bitrates by a clear margin. A bare .aac file is the raw ADTS stream rather than the .m4a container most software expects.
Where you run into it: YouTube and streaming audio tracks, broadcast, anything that came out of a device rather than a music shop.
What it costs you: The naked .aac extension confuses a surprising amount of software, which is the usual reason people convert it.
Worth understanding what you are about to do to your metadata, because this pair is the starkest case of it on the site. A FLAC is the best-documented audio file you are likely to own: artist, album, track number, date, comments, cover art, and a stored checksum of its own contents. A bare .aac is the least-documented — it is a run of encoded frames with no container, so it has nowhere to put any of that, and nowhere to record its own length either. The audio comes across at whatever rate you pick. Everything written around the audio does not.
Convert to M4A instead unless you have a specific reason not to. It is the same AAC audio inside an MP4 container, it costs a few kilobytes more, and it carries your FLAC's artist, album and title straight across — which this page cannot. The only good reason to be here is that something downstream insists on an ADTS stream, meaning broadcast and streaming tooling rather than anything a person opens. If you are moving a music library onto a phone, you are one page away from the right answer.
Yes, entirely, and there is no cap on how many files you convert. No account, no watermark, no trial.
Yes, and Best here means a flat 192 kbps rather than a variable setting, so the encoder holds that rate through dense and quiet passages alike. From a lossless source AAC at 192 is a strong result — it is the most efficient of the four codecs here. The loss that will actually bother you on this pair is not audible, though. It is that the file arrives with no title, no artist and no artwork, and a player showing an unknown duration that refuses to scrub.
About a fifth of the FLAC, and predictable to the second because the bitrate is fixed: four minutes of stereo is close to 5.5 MB whatever the music does. A raw stream carries no container at all, so it comes out slightly smaller than an M4A of identical audio — and that difference is precisely the tags, the artwork and the seek index you have given up.
Yes — AAC is one of the formats this converter writes, so the reverse page exists at /aac-to-flac/. Be clear about what comes back, though: the FLAC you get is a faithful copy of the AAC, not of the original. The loss happened on the way out, and returning to a lossless format stops further loss rather than undoing it. Keep the original FLAC if you still have it.
The file is uploaded to do the conversion — nothing here runs in your browser — and both your upload and the converted result are deleted the moment the file is sent back. Nothing is stored and nothing is logged beyond the request itself.